Production of pulp molded articles includes the step of dewatering a water-containing preform as obtained by a papermaking operation for the purpose of, for example, improving handling properties and shortening the drying time. A known dewatering method comprises interposing the preform between an outer mold of which the inner shape is substantially the same as the contour of a molded article to be produced and an inner mold having a flexible film which expands into a shape substantially the same as the inner shape of the molded article and pressing and dewatering the preform by making use of the expansion of the flexible film as described in JP-A-7-223230.
In the above method, if the water-containing preform is out of the right position when pressed between the outer mold and the inner mold, or if the preform has an uneven thickness, it could follow that the preform, being fragile, is deformed or undergoes damages such as fall-off of the pulp fibers making up itself due to missregistered contact with the molds.